(1) Field of the Invention
The present invention relates to a method and apparatus which provides multiple, sequential radiofrequency wave processing modes for material treatment. In particular, the present invention provides a method and apparatus wherein a material is automatically processed in resonant modes which are most favorable to each stage of processing of the material.
(2) Prior Art
It is believed that the closest prior art is described in U.S. Pat. No. 4,777,336 to Asmussen, one of the present inventors. This patent describes a single mode resonant radiofrequency wave applicator (preferably microwave) used for material treatment which can be used in the present invention. This invention works well; however, single mode treatment may not be sufficient for materials which have multiple phases which are transient, such as filled uncured resins. A problem is that the prior mode in the applicator must be completely extinguished when a new mode is begun to prevent uncontrolled processing and the time sequencing of the modes must be controlled to produce the desired heating patterns. There is a need to provide multiple modes over time in the applicator in order to achieve controlled processing of materials.